Scott, is this for a BP?
If so, you may want to use a UTH for a hotspot and just use the rhp for the ambient temp. Both units should run on a t-stat though. But BPs and boas too benefit from the belly heat a uth will provide. But there are many who just use an rhp so it does rather depend on your preferences.
One thing to keep in mind is that BPs like to hide. An rhp heats like the sun - it warms the surface under it. If the rhp is set up at one end for a warm side and there's a hide box under it, the
top of the box will heat nicely, but
inside the box will not be very hot at all. That's why a uth would be beneficial for a BP.
I use my rhp for my GTP which uses perches to get close to the unit and that's the hot spot. I love it - it's a great product! But I wouldn't use just that for my BP - she'll always have a uth simply because of the hide boxes. One day when my boas are big enough for their adult enclosures, I will probably use rhp - but boas don't absolutely need hide boxes the way BPs do.
Personally, I would set up a 2x2x2 pvc cage with the rhp in the center to heat the ambient temps and place a uth on one end for the hotspot. Put both units on a dual control t-stat such as the VE300 x2 or the Herpstat 2 and you'll be good to go!!
These are just some thoughts to consider......